Sudoku Collector
Every puzzle is named for the move it teaches. The Train button teaches the technique before it shows you the step — and you can bring any puzzle from anywhere and have it taught with the same machinery as the built-in packs.
No ads. No accounts. No tracking. Works offline.
Found a hard one in a magazine, on a website, in a friend's screenshot? Paste it or tap it in. The app checks it has one solution, works out what it teaches, and lands it in your Dossier — playable with the full hint train, forever.
Guided hint trains explain why each move is the move, in plain language. The solver runs against your live board on every tap, so the hint is never stale even if you solved part of it a different way.
Nothing is labeled a vague "Hard." Each puzzle carries the hardest technique it requires — Naked Pair, X-Wing, Swordfish, all the way to Bowman's Bingo — so you always know what you're practicing.
No advertising, no in-app purchases, no sign-in, no analytics SDK, no crash reporter, no push notifications. It works fully offline. Nothing about how you play leaves your phone.
Most Sudoku apps treat puzzles as a difficulty commodity. Sudoku Collector inverts that — every puzzle is hand-classified by the technique it teaches, and the Train button teaches that technique before it shows you the move.
From Naked Singles to Bowman's Bingo.